In certain mechanisms, lost motion can result in severe problems and performance penalties. An example is in an aircraft control system where typically a cable arrangement, actuated by the pilot, causes movement of certain links and levers to move an aircraft control surface. Aerodynamic forces on the control surface can result in severe vibrations in the mechanism when lost motion is present. In the absence of a backlash eliminating device, nothing in the system can resist oscillations which operate through the clearance present in the mechanism.
Backlash also can be a problem in various kinds of linkages and mechanisms other than aircraft controls, where precise movement is necessary, particularly movement in two directions.
A problem can arise with a backlash elimination device from misalignment of the input and output forces applied to it. Generally speaking, it is impossible to build a system in which the forces on a link are exerted in a plane that precisely includes the longitudinal axis of the link. Some lateral forces are inevitable. Such lateral forces applied to a backlash eliminating device can result in binding of the moving components and malfunctioning of the device.